Commercial alumina templates as base to fabricate 123-type high-T _c superconductor nanowires

Abstract

Nanowires of high-T c superconductors of the RE-123 type (RE ¼ rare earths) were grown by the anodized alumina template method, employing commercially available alumina templates with nominal pore diameters of 20 and 100 nm. Pre-reacted YBa 2 Cu 3 O x (YBCO) and NdBa 2 Cu 3 O x (NdBCO) powder was molten on top of the templates in order to fill the pores with the 123-type material. The resulting samples were oxygen-annealed at 450 8C. Superconductivity with a transition temperature of 88 K (YBCO) and 96 K (NdBCO) was confirmed by means of magnetic susceptibility measurements (SQUID) using pieces of the filled template. The electric (resistance) and magnetic measurements revealed further relatively sharp superconducting transitions. To understand the dimensions of the resulting nanowires (length up to 10 mm, diameter between 100 and 250 nm), which do not correspond to the nominal pore diameters, the empty and filled commercial templates were analyzed in detail by scanning electron microscopy. We discuss the feasibility of this approach to produce larger amounts of nanowires.

Facile Preparation of Gold Nanoparticles Silica Composite Film Embedded in Anodized Aluminium Oxide-Glass Substrate

“…This might indicate that the infiltration of the sol-gel inside the porous structure of AAO resulted in a higher stability of thin film sample. However, as the commercial AAO substrates did not have a bottom part [19], some portion of the drop-casted nanocomposites leaked out from the AAO bottom. Furthermore, the brittleness of AAO substrate also limited the characterization or practical usage of the films.…”

Fabrication of Superconducting Nanowires Using the Template Method

“…Thus, we attempted to grow YBCO and NdBa Cu O (NdBCO) nanowires using the anodisc templates, and the results were published in Refs. [ 41 , 76 , 77 ]. Pre-reacted YBCO and NdBCO powders were employed, ground to an average particle size of about 1 m by ball-milling.…”

“…A typical result of our analysis is shown in Figure 7 . The size of the pores in the commercial templates is always ∼100 nm (the pore diameters on the top surface tend to be somewhat smaller as at the bottom surface, and, in the center section, the pore size is much larger [ 76 ]), and only some constrictions in the center of the template define the smaller nominal diameter, as indicated by arrows. Thus, we have to conclude that the pore diameters measured were mostly larger than the nominal values, especially for the templates with a nominal pore diameter of 20 nm.…”

“…After several unsuccessful experiments, the YBCO nanowires could be separated from the AAO template by chemical etching with a 4 mol/l NaOH solution (holding time for at least 1 h). The diameter of the nanowires is not homogeneous [ 76 ], but the pieces of the nanowires obtained are free of cracks. The length of the nanowire pieces is typically about 2–10 m.…”

NbN superconducting nanonetwork fabricated using porous silicon templates and high-resolution electron beam lithography

“…The synthesis of nanostructures based on robust self-assembled nanoporous templates recently received a growth of interest. This bottom-up technique allows one to fabricate, with high reproducibility, a large number of nanostructures in a single-step process [1][2][3][4]. In particular, the deposition of ultrathin films of superconducting materials on templates, both porous alumina and porous silicon (PS), as well as on inorganic membranes, gives the possibility of creating interconnected nanowire networks where commensurability effects [5][6][7], or properties typical of a single superconducting nanowire are observed [8][9][10].…”